Improvement in dentists  chairs



IL PEi'ERS. PMOTOLUTHOGRAPHER WASHINGTON D C iure' STATES I. A. SALMON, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT IN DENTISTS CHAIRS.

Specification forming part of Letters Patent No. 55,36S, dated .I une 5,' 1865. l

To all whom it may concern:v

Be it known that I, IRA A. SALMON, of Boston, in the county ot' Sut'l'olk and State of Massachusetts, have made a new and useful Invention having reference to Operating-Chairs for -the use ot' Dentists, and I do hereby declare the saine to be fully described in the following specification, and represented in the accompanying drawings, of whichl Figure l is a side elevation of one of my improved chairs. Fig. 2 is a vertical and longitudinal section of it. Fig. 3 is a vertical and transverse section of it. Fig. 4 is an inner side view of the scroll-wheel used with the rack for elevating the seat. Fig. 5 is a rear elevation ot the chair. Fig. Gis a vertical section, and` Fig. 7 is a horizontal section, of the head-rest hinge, each of such sections being taken in line with the axis ot' the hinge-pin composing part of the clamp.

Operating-chairs as usually made for den tists have their body connected with the footstand by means ot' a ball-and-socket joint. In constructing a chair I have sought to avoid the ball-and-socket joint on account of the uncertainty incident to it of securely holding the body in any position. It will readily be seen that any failure to hold the body firmly may bethe cause of serions accident to a patient, for as the dentist, while operating on a person, frequently has to exert great pressure on the body of the chair, it should be very strongly held in position whatever ina-y be its inclina tion.

For supporting the body of the chair on its foot-frame or base I employ girnbals in lieu of a balland-socket joint, and with such gilnbals I also employ certain curved bars and bolts. Thus I do not depend upon the friction ot' any surfaces for holding` the chair-body in position, but make use of that in which there is absolute certainty of securely holding it so that any ordinary force exerted on it by the dentist while operatin g on the teeth or mouth ot" a person seated on the chair will not accidentally throw the body of the chair out of its position. v

In the drawings, A denotes the base or foot frame, B the body, C the seat, D the foot-rest, and E the head-rest, of the chair, such being the constituents of an ordinary operating-chair.

The base A has two curved standards or posts, a a., projecting upward from it, and

horizontally, so as to enter boxes or bearings c c, applied to a ginibal-ring, d, arranged beneath the chair-body and the seat.

The said gimbal-ring has also two journals, c c, extending from itin opposite directions and in a line at right angles with that of the two journals b b. These journals c c of the girnbal-rin g enter bearin gs f j', extendiitg from the lower part of the chair-body.

Furthermore, there projects down ward from the giinbal-ring, and directly underneath the rearinost journal, a curved bar, g, having a series of holes, It h h, made through it or arranged in manner as represented. A slidebolt, z', supported by the base-frame, operates with such bar, and is so connected with a foot lever, lc, arranged in the base-frame in manner as shown in the figures, as to be capable of being moved by such lever either into or out of one of the holes L, which may be brought into position for reception of the bolt. Another such curved bar, l, extends down from the chair-body, and at a plane at right angles with that in which the bar g is disposed.

A slide-bolt, m, provided with an actuatinglever, a, operates with the holes ofthe second curved bar, l, such bolt and lever being duly lsupported by a bracket, 0, projecting down from the gimbalring.

The foot-rest D is supported 011 two arms, P P, formed as represented, and hinged at their rear end to thel chair-body. These arms l are connected by a cross-bar, q, which operates with two curved racks, r r, which depend from and turn on a cranked shaft, s, extending laterally across and supported on the chair-body. A bar',l t, unites the two curved racks, and has a rod, u, extending back from it and through the rear part of the body of the chair, such rod being provided at its rear end with a knob,o. Aband,w, connected tothecross-barq and extended upward and fastened to the shaft s, enables the foot-rest te be raised or lowered by a person by applying his hand to and turning a crank-the crank w of the shaft s. The two racks r r serve to rinly support the foot-rest at any altitude at which it may be placed within its limits of motion.

Extending across the chair frame and underneath the seat is a strong metallic crossbar, y, down through which a rack, z, projecting from the seat, slides freely.

A wheel, c', provided with a scrollflange,

b', formed and projecting` from its side in manner as shown in Figs. 2 and 4, 'is arranged within the bar y and upon a shaft, c', supported on the bar and chair-body and arranged thereon in manner as shown in Figs. 2 and 5. A crank, d', is fixed 011 the outer end of the shaft e. The scroll of the wheel a 4engages with the rack, so that during each entire revolution of the wheel the rack will be -moved by it a distance equal to that between the centers of an)T two next adjacent teeth of such rack.

The advantage of a scroll 'and rack over a screw operated by a shaft and bevelgears is that it is not so expensive to make and has less surface to keep lubricated, and besides they operate with little or no noise such as is incident to gears, Y

The head-rest E is supported on an arm, c', projecting from a cylinder, f', in manner as represented in Figs. l, 2, and 5. The headrest slides longitudinally on the arm and is provided with a clamp-screw, g', to secure it to the arm.

The cylinder j" rests and turns in a bearing, h', which in turn is supported on the upper part of a vertical adjuster, i. A cylindrical pin, k', goes longitudinallythrough th-e cylinder, which is recessed at its middle, as represented at Z.

A clamp-screw, m', goes up through a crossslot, n', made in the head ofthe adjuster 'i' in manner as shown in Fig. 6, the said screw being provided wit-h a shoulder at o" to bear against the said head. The screw, after going through the bearing, screws' into the pin k laterally, and thus the pin is not only made to serve as part of a hinge, but as part of a clamp toprevent the head-rest from turning hack on the hinge formed by the bearing, the cylinder, and pin.

By having the notch in the cylinder and` the cross -slot in the head of the adjuster the head-rest may be moved laterally, or forward and backward, and adjusted in position to excellent advantage.

a toothed sector inv determining the degree of l inclination of the head-rest, and thereby limits the head-rest to afewpositions only, whereas my improved joint enables the head-rest to be adjusted to any desirable angular position with the plane of its movement. Therefore,

l claiml. The arrangement of the gim bal ring d, the

journals b b e e, bearings c 0 f f, curved bars g l, and their bolts t m with the chair-body B and the base or foot frame A.

2. rEhe arrangement and combination ofthe movable foot-board, supprting-racks r r, and their operative sliderod n, with the chairbody B, the foot-board supporting'arms p p, their cross bar t, and the crank sha-ft s, and band w, for raising and lowering the foot-board, as specified. Y

3. The mechanism for adjusting the elevation of the chair-seat, the same consisting of the wheel c', with its scroll-flange b', the rack z, and the carrier y, arranged and combined with the seat and the chair-body substantially as set forth.

4. The improved head-rest hinge-joint as made of the recessed cylinder f', the pin 7c', the clamp-screw m', and the bearing h', constructed and arranged together as speeitied.

5. The combination of the cross slot n' in the adjuster with the clamp-screw m and the head-rest E, applied together substantially as described.

I. A. SALMON.

Witnesses:

R. H. EDDY, F. P. HALE, Jr. 

